Dear Editor, This letter presents a coverage optimization algorithm for underwater acoustic sensor networks (UASN) based on Dijkstra method. Due to the particularity of underwater environment, the multipath effect and channel are easily disturbed, resulting in more node energy consumption. Once the energy is exhausted, the network transmission stability and network connectivity will be affected. Coverage optimization is a key problem in UASN, which directly affects the network lifetime. Considering the complexity of underwater acoustic channel, the energy transfer model is improved in this paper. Dijkstra algorithm is used to transform global optimization into inter node optimization to achieve optimal coverage. The feasibility and complexity of the algorithm are analyzed. Simulation results show that compared with similar algorithms, this algorithm can achieve better network coverage, which prolongs the network lifetime and improves the network performance effectively.